After seeing the responses in my original thread on the topic, we've decided to use a hybrid rocket design for the kart. At this point, we're still in a design phase, and the actual construction won't start until July, but here's what we have so far:

Body:
This thing's essentially a very large engine with 4 wheels and a guide on the bottom to keep it on course. The frame will be built from structural aluminum tubing and welded, and we think we can keep its total weight well under 200 pounds, probably a lot less that that.

Guidance:
Rings on the bottom, which a steel cable is passed through. The cable will be anchored at the height of the rings off the ground and tensioned, causing minimal friction during normal operation.

We're melting down steel for the rocket casing using charcoal being burned by a high pressure, high volume, high flow air supply, with supplemental oxygen for throttling the burn rate. The steel will be melted down in high temperature rated ceramic containers in 5L batches, then poured down to the bottom of the concrete mold. After the whole thing is cast, we wait for it to cool, and then smash away the brittle concrete, which will have been severly weakened by the molten steel. The outside can be done with a sledgehammer, and the inside will use slightly more creative means.

Valving should be a minimal concern, as this thing won't have any throttling capabilities whatsoever (or any steering, braking, or overpressure safeties ).

This thread will be kept updated with details of the build. Input from any of the resident rocket scientists is, as always, greatly appreciated.

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Spudfiles' resident expert on all things that sail through the air at improbable speeds, trailing an incandescent wake of ionized air, dissociated polymers and metal oxides.

Hmm i was thinking way higher than that, but im no rocket sciencetist. Who will be "driving" this you or will you get another poor soul to test it out. Also where will you be driving this you must have soe very long stretch of lightly used road near you.

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Coodude26 wrote:
People who laugh really hard at stuff that pisses you off/you getting hurt, who then say "I'm sorry, I can't stop" but you know they easily could.

Mr.C: That's not as easy as you think. It's like me kicking you in the balls and telling you to stop crying.

It will be on a long stretch of private road. We've got lots of volunteers who don't seem to care that they might get smeared all over the road. The owner might not like that very much, but any remains would be so charred that we could probably scrape them up pretty easily. Of course, someone would start asking questions eventually...

And as for stopping: It'll stop when it's damned good and ready

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Spudfiles' resident expert on all things that sail through the air at improbable speeds, trailing an incandescent wake of ionized air, dissociated polymers and metal oxides.

Hmmm let's see here....no throttle, no steering, no brakes, no safeties...basically straddling a NOS/paraffin bomb... ...I'm voting with the unmanned crowd, at least until a few "proving runs" are performed.

Did you happen to catch the Mythbusters NOS/paraffin confederate rocket episode? The burn and acceleration on that thing was vigorous to say the least. They also did a followup episode where a NOS/meat rocket detonated on the launch pad.

Considering the risks, are you sure this particular form of locomotion is really that worthy an experience?

You're going to have problems with casting the steel. Which problems, exactly, I can't say, but you'll have problems (I know from personal experience).

As for overall "danger" factor, I'd give this about a 6/10 unmanned, and 37/10 manned.
A rocket that size could get the thing moving more than 100 mph, but how much more, I can't say. You're going to have get some solid numbers down before much experimentation is done.

Apparently the concrete mold would have a strong likelihood of exploding violently and spraying molten steel everywhere because of bubbles of water that could be trapped in it. So, we'll use a specifically designed high temperature casting compound instead of concrete.

As for overall "danger" factor, I'd give this about a 6/10 unmanned, and 37/10 manned.

A 370% chance of at least one violent death? Sounds about right. But we'll have quite a few people at the launch, and I can almost guarantee that the 3.7 of them that die won't include me.

Considering the risks, are you sure this particular form of locomotion is really that worthy an experience?

What could be more worthy an experience than a group of 4 teenagers spending thousands of dollars to make a horribly dangerous rocket cart that can kill them in 42 different ways at any given time without warning, and will probably explode violently on ignition?

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Spudfiles' resident expert on all things that sail through the air at improbable speeds, trailing an incandescent wake of ionized air, dissociated polymers and metal oxides.

DYI wrote:What could be more worthy an experience than a group of 4 teenagers spending thousands of dollars to make a horribly dangerous rocket cart that can kill them in 42 different ways at any given time without warning, and will probably explode violently on ignition?

so a 4 inch schedule 160 pipe is the shape of a rocket motor?
Last time I checked it was the shape of a pipe, and didn't have a nozzle or cap on the other end.
Feel free to correct me if I am wrong, but I also doubt that it would be strong enough to hold a rocket engine...
Think, then post.

oh ya, and I don't think 4" pipe has an INSIDE DIAMETER of 4.5"...

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